Emergency crews on Tuesday struggled to contain deadly wildfires that have scorched hundreds of square miles of land in four states and forced thousands of people to flee their homes ahead of the wind-whipped flames.

The fires were burning in parts of Kansas, Oklahoma, Texas and Colorado, and warnings that fire conditions were ripe were issued for Iowa, Missouri and Nebraska, as powerful thunderstorms moved through the nation's midsection overnight, spawning dozens of tornadoes, according to the National Weather Service. The fires have killed at least five people.

In Kansas, wildfires have burned about 625 square miles of land and killed one person. The Kansas Highway Patrol said Corey Holt, of Oklahoma City, was killed Monday. His tractor-trailer jackknifed as he tried to back up because of poor visibility on highway 34 in Clark County, and he succumbed to smoke after getting out of his vehicle. Two SUVs crashed into the jackknifed truck, injuring six people who were taken to hospitals, state trooper Michael Racy said.

About 545 square miles of the state's burned land is in Clark County, which is on Kansas' southern border with Oklahoma. Thirty structures, including some homes, have been damaged in the county, said Allison Kuhns, a spokeswoman for the county's emergency management office. About half of those structures were near the small city of Englewood, which was one of two communities evacuated. Kuhns said there also have been significant cattle losses and that there were entire ranches that were engulfed.

Elsewhere, the largest evacuations were in Reno County, where 10,000 to 12,000 people voluntarily left their homes Monday night, said Katie Horner, a spokeswoman for the state's Department of Emergency Management. She said 66 people from the area were in shelters Tuesday in Hutchinson, which is 40 miles northwest of Wichita.

Among them was Shelley Wilson, who fled with her disabled son and pets from a blaze Monday that was encircling her farm outside of Hutchinson. She returned later that night with her adult daughter to retrieve her tractor.

“I don't know if I have a home to go home to,” Wilson said at the shelter Tuesday as her daughter did her best to lighten her mood. “In case I needed to rebuild, I wanted to at least have my tractor.”

Several hundred more people evacuated their homes in Russell, Ellsworth and Comanche counties, which are in central Kansas.

The Kansas fires forced the closure of some roads, including two short stretches of Interstate 70, the main highway that cuts across the state from Colorado to Kansas City.

In the Texas Panhandle, three fires have burned more than 195 square miles of land and killed at least four people. One of the blazes near Amarillo threatened about 150 homes, while a larger fire in the northeast corner of the Panhandle near the Oklahoma border was only 5 percent contained as of Tuesday morning, according to Texas A&M Forest Service. That larger fire was responsible for a death on Monday, authorities said Tuesday without providing further details.

A wildfire in Gray County, which is also in the Texas Panhandle, killed three ranch hands who were trying to usher cattle away from the flames, said Judge Richard Peet, the county's head administrator. One of the three apparently died of smoke inhalation Monday night and the other two were badly burned and died on the way to hospitals, he said.

Forest Service spokesman Phillip Truitt said as many as four firefighters were hurt battling the fires Monday. He provided no details on their conditions Tuesday morning.

In northeastern Colorado near the Nebraska border, firefighters lost ground to a blaze in rural Logan and Phillips counties. They had the blaze 90 percent contained Monday evening, but only 50 percent contained Tuesday, despite working overnight to douse hot spots and flare-ups. The fire has burned more than 45 square miles of land and destroyed three homes. Nearby residents were warned to be ready to evacuate if the fire advances toward them.

More than 70 firefighters from 13 departments battled the blaze, which was reported east of Sterling on Monday morning. The fire, which was driven by wind gusts of nearly 50 mph, jumped Interstate 76 and spread into Phillips County.